#1
hey guys.
yesterday my amp started acting funny. i noticed that the clean channel was slightly distorted, and before long it was losing volume, but the lead channel seemed unaffected so i presumed it couldnt be anything too serious. today i went to play and things are worse. the clean channel is almost inaudible and there was a significant drop in the gain on the lead channel.
im gonna presume that the problem is preamp valves, but the valves are JJs that are only about 4 months old, and none seem to be glowing any differently to the others.
help!
Ibanez RGT42FM w/duncans
Musuc Man JP6, fully loaded
Crybaby 95Q
Boss DD6
Mesa DC-5
#2
the power amp valves are probably going bad
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Moen Jimi Vibe
Danelectro Cool Cat Fuzz
Zvex Vexter Fuzz Factory
VHT 2x12 w/ V30's
#3
btw, the poweramp valves are the same age.
i would have thought that if it was the power amp valves it would have affected the volume on both channels pretty much equally, no?
also, the vast majority of my gain is preamp gain, so i wouldnt have expected this much of a gain drop if it was a poweramp problem.
im pretty much a valve noob and i have know doubt uv forgotten more about valve amps than i know, but this is just what i would have thought...
Ibanez RGT42FM w/duncans
Musuc Man JP6, fully loaded
Crybaby 95Q
Boss DD6
Mesa DC-5
#4
It does sound like some sort of valve problem. I'd take it to an amp technician and see what he thinks. I know some people might see me recommending that people take their amp to technicians a lot but it's the best thing to do IMO.
#5
Dodgy valves? Perhaps one cracked? I don't know much on the subject of amp maintenance but I do know that quite a few valve amp problems in the area of volume drops are caused by problems with the valves.
#6
At first I thought it must be a preamp problem, but if both channels are going it could well be your power valves.
However 4 months is very short, so it's possible one of the shared AX7s has gone, possibly the phase inverter. I can't see how the valves could have reached their lifespan after 4 months unless the amp was incorrectly biased - DCs are self-biasing so it's not likely!

Try switching the preamp valves around a bit to see if you can trace the problem back to an individual valve. If you've got your old power valves, try sticking them in to see whether it's the power section at fault. If not - amp tech!